Should one pay off one'e home mortgage ?

If one has the money should one pay off one's home mortgage ?

Under what circumstances should one:
-pay off the mortgage
-NOT pay off the mortgage

What are the tax negatives and positives ?

My sister is in this situation. I think they are in the 20 to 28% tax
bracket. Have reasonable income. Ages around 47 and 50.

Is there an article, website that has written a good article on this
topic ?

I am sure a lot of people would like an answer to it.

Thanks
Ava